This invention relates to a motor, and more particularly to a motor with a rotor having five slots located inside of two magnets.
A related motor is shown in FIG. 6. A motor 1 as shown is schematically constructed of a motor case 2, two arc-shaped magnets 3 arranged so as to face each other within the motor case 2, a spring 4 for pressing to fix the two magnets 3 to projections of the motor case 2 and a rotor (motor core) 5 arranged inside the two magnets 3. The rotor 5 has five slots 6 which are arranged at regular intervals in a rotating direction.
The motor 1, as shown in FIG. 6, is designed so that the circumferential angle for the inner peripheral portion of one of the arc-shaped magnets 3 when viewed from a rotating center C according to the center of the motor case 2, i.e. the magnet inner circumferential angle θ is 135° (for example, JP-A-11-341722).
Since the above two-pole five slot motor 1 is designed to provide the magnet inner circumferential angle of 135, the magnetic flux density greatly varies at opposite ends in the circumferential direction of the magnet 3. As a result, a cogging torque which leads to the irregular rotation of the motor 1 is increased. This is a serious problem from the standpoint of view of assuring the accuracy of driving control and rotation driving of the motor 1.